This avalanche advisory is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This advisory covers the Central Sierra Nevada Mountains between Yuba Pass on the north and Ebbetts Pass on the south. Click here for a map of the forecast area. This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.


This Avalanche Advisory was published on April 15, 2009:

April 15, 2009 at 6:50 am

For most areas, avalanche danger is LOW for all elevations and aspects. Normal caution is advised. Pockets of MODERATE danger exist in the mountains directly south of Lake Tahoe near and above treeline on SE-S-SW aspects, 37 degrees and steeper.

Forecast Discussion:

Snow showers are lingering over the forecast area this morning as a cold front slowly exits the region. In most areas, new snowfall amounts measure a trace to 1 inch. In the mountains directly south of Lake Tahoe, north winds are contributing to lake effect snowfall that has deposited 3 to 4 inches of new snow. An additional 1 to 2 inches of new snow is expected to accumulate in this area through the morning hours. Remote sensors throughout the forecast area are reporting air temperatures in the single digits and teens this morning. Ridgetop winds have shifted from southwest to west to north over the past 24 hours. Continued moderate north winds during the day today are expected to keep air temperatures below freezing.

Yesterday, observation made on Castle Peak (Donner Summit area) revealed that cool air temperatures kept snow surface melting on southerly aspects to a minimum. Many areas remained frozen all day. In areas near exposed cliff bands where the snowpack received more heating, the top 1/2 inch of the snowpack was wet at 8,400' at 12:30 pm. Northerly aspects continue to hold a stable snowpack with shallow snow on top of a supportable crust in wind protected areas above 7,500' to 8,000'. Below 7,500', breakable surface crust conditions exist.

Today, colder air temperatures are expected to keep snow surface melting on southerly aspects to a minimum, with many areas remaining frozen all day. In the mountains directly south of Lake Tahoe, 4 to 6 inches of new snow is expected to accumulate by mid day. Expect to find pockets of unstable slab formation near and above treeline in wind loaded areas, mainly on steep SE-S-SW aspects. Human triggered avalanches involving slabs up to 1 foot deep are possible. Snowpack failure is expected to occur on top of the upper most crust or within the new snow in these areas.


The bottom line:

For most areas, avalanche danger is LOW for all elevations and aspects. Normal caution is advised. Pockets of MODERATE danger exist in the mountains directly south of Lake Tahoe near and above treeline on SE-S-SW aspects, 37 degrees and steeper.


Brandon Schwartz - Avalanche Forecaster, Tahoe National Forest

Weather Observations from along the Sierra Crest between 8200 ft and 8800 ft:

0600 temperature: 8 to 10 deg. F.
Max. temperature in the last 24 hours: 20 to 24 deg. F.
Average wind direction during the last 24 hours: Southwest shifting to north.
Average wind speed during the last 24 hours: 23 mph
Maximum wind gust in the last 24 hours: 60 mph
New snowfall in the last 24 hours: Trace to 4 inches
Total snow depth: 136 inches

Two-Day Mountain Weather Forecast - Produced in partnership with the Reno NWS

For 7000-8000 ft:
  Wednesday: Wednesday Night: Thursday:
Weather: Mostly cloudy skies with isolated snow showers in the morning. Scattered snow showers in the afternoon. Partly cloudy skies with scattered snow showers in the evening. Isolated snow showers after midnight. Sunny skies.
Temperatures: 22 to 29 deg. F. 15 to 22 deg. F. 41 to 48 deg. F.
Wind direction: N N N
Wind speed: 10 to 15 mph increasing to 15 to 25 mph with gusts to 35 mph in the afternoon. 10 to 15 mph with gusts to 30 mph in the evening. Around 10 mph.
Expected snowfall: Trace to 2 in. 0 to trace in. O in.

For 8000-9000 ft:
  Wednesday: Wednesday Night: Thursday:
Weather: Mostly cloudy skies with scattered snow showers. Partly cloudy skies with scattered snow showers in the evening. Isolated snow showers after midnight. Sunny skies.
Temperatures: 21 to 27 deg. F. 14 to 21 deg. F. 39 to 45 deg. F.
Wind direction: N N N
Wind speed: 15 to 25 mph with gusts to 40 mph. 10 to 15 mph with gusts to 35 mph. Gusts decreasing to 25 mph after midnight. 10 to 15 mph.
Expected snowfall: Trace to 2 in. 0 to trace in. O in.